Pick a character who has a move that takes time to animate. Like Ganondorf. Try knock the bag into the air and get it to land on nearby ground in front of the initial platform. Just be sure to have your character standing near the place where it will land. Charge your move a split second before it lands. With good timing, the game will think that you're done, and the score will get closer as it always does at the end. But if the bag is beaten up enough, it will still be moving in the air. The game may even exit the contest while the bag is still flying and while the distance is still increasing.